I like All Seeing Eye still, but that is v2.6, probably before Yahoo bought it out. Not sure how the new versions are.
After QuakeSpy and early versions of Gamespy, that piece of software (Gamespy Arcade) went to complete crap. It's so annoying when some games make you use it to play online.
So if you don't like Gamespy Arcade or newer versions of All Seeing Eye, perhaps
Xfire
Pre-Yahoo/earlier version of All Seeing Eye
Qtracker. This one looks good and simple, it's freeware and at version 4.52 so it looks fairly mature and has a good amount of features. It says it supports around 100 games, and you can find the list in the forums. It's almost all FPS, but I'm not sure if that is due to the game developers. It seems most racing, simulation, and other games require Gamespy Arcade, if they don't have built-in browsers. You can also buy Qtracker for $20, but I don't see what the incentive is other than you will get free upgrades and features if it ever turns into shareware. Seems more like a donation.
Actually, I just found this wiki article, check them out and let us know what you like the most (not a whole lot of options, but a few look good enough)
Game server browser
edit: Really, looks like its earlier versions of All Seeing Eye (as long as they didn't disable access with them), Qtracker, or HLSW, with the latter two looking quite similar and having a very similar compatible game list.